The HP TouchSmart 520 touchscreen driver for Windows 8 with the following hardware ID:

USB\VID_1926&PID_1840&REV_0008&MI_00

Does not exist! There is no driver for the touch screen on the HP TouchSmart 520 PC. A Windows 7 driver (that won’t work on Windows 8) can be downloaded from the HP website, under the Windows 7 drivers-original list.

Addendum: There is a driver for this, it’s available as an optional update through Windows Update.